Heteronuclear radioisotope nanoparticle of core-shell structure and preparation method thereof

ABSTRACT

Heteronuclear radioisotope nanoparticle of core-shell structure and a preparation method thereof are provided. The Heteronuclear radioisotope nanoparticle of core-shell structure comprising core of two different radioisotopes selected from a group consisting of  198 Au,  63 Ni,  110m Ag,  64 Cu,  60 Co,  192 Ir and  103 Pd, and a shell comprising Si0 2  surrounding the core. 
     The Heteronuclear radioisotope nanoparticle of core-shell can be used as a tracer for the purpose of detecting variation of volume ratio or for the evaluation of the behavior characteristic of a water resource, based on information about phase ratio in the flow of multiphase fluid existing in a process which is operated under extreme condition such as high temperature and/or high pressure conditions.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application claims the benefit of priority from KoreanPatent Application No. 10-2011-0101302, filed on Oct. 5, 2011, thecontents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heteronuclear radioisotope nanoparticleof core-shell structure and a preparation method thereof.

2. Description of the Related Art

Radioisotope refers to a matter in which atomic nucleus thereof emitsradioactive rays without requiring external influence such as pressure,temperature, chemical treatment, to turn into different type of atomicnucleus. The generally available radioisotope includes ¹⁹⁸Au, ⁶³Ni,^(110m)Ag, ⁶⁴Cu, ⁶⁰Co, ¹⁹²Ir, or ¹⁰³Pd.

In the industrial application, open radioisotope generally serves as atracer. That is, by tracing radioactive rays emitted from theradioisotope by a measuring device, it is possible to analyze thebehavior of a material. Since gamma (y) ray does not carry electricitynor does it have mass, this has less interaction with the matter andless energy loss when passing through the matter compared to the otherradioactive rays. Further, since γ ray has strong penetrating powerirradiated from the radioactive nanoparticles, this can penetratethrough the wall of the vessel containing the fluid to easily detect thetarget of detection existing in the fluid.

The metal nanoparticles are generally made by electric bombardment,sodium/halide flame and encapsulation technology (SFE), chemicalreduction, or electric reduction. However, the metal nanoparticles madeby these methods have rather irregular granularity of the particles, andmass production is rather difficult at room temperature. Meanwhile, theradiation reduction relates to irradiating radioactive ray onto metalion solution and generating metal nanoparticles using free radicalsgenerated from the solution. This method has the advantages of no sidereaction, and mass-productability at room temperature. By way ofexample, Reference 1 (S. H. Choi et al.) report about fabricatingprecious metal nanoparticles using radiation reduction, and using theseas catalysts. Further, S. H. Choi et al. have conducted a studyregarding radioactivation of the nanoparticles by irradiating neutronsthereon. Further, Reference 2 (S. D. Oh et al.) researched about loadingprecious nanoparticles in a carbon nano-tube to use as a fuel battery,in which the researchers studied about synthesizing nanoparticle alloy.

The researchers of References 1 and 2 used surfactant or soluble polymeras colloid stabilizer or nanoparticles loaded in a specific carrier tostabilize the nanoparticles. However, in fabricating radioactivenanoparticles, there is a risk that the colloid stabilizer itself can beactivated. Therefore, it is required that the use of colloid stabilizerbe minimized or the stabilizer be completely eliminated after use, inorder to use the radioactive nanoparticles as a tracer. However, if thecolloid stabilizer is eliminated in the fabricating process of the metalnanoparticles, aggregation can occur among the nanoparticles due toconsiderably low mass ratio to surface area, and as a result, thenanoparticles grow and cannot serve as a tracer for flow detection of atarget of the research. In order to overcome the problem explainedabove, a technique to coat the metal nanoparticles with SiO₂ which isnot activated even by the radiation of the neutron (Reference 3).

Meanwhile, Reference 4 (C. P. Winlove et al.) studied about attachingiodine-125(¹²⁵I) as radioisotope to gold (Au) nanoparticle and mixingwith natural polymer such as protein peptide to use this as a tracer.However, in implementing this to high temperature and high pressureindustrial process, there is a problem that the radioisotope (¹²⁵I) isseparated from the gold nanoparticle. Further, Reference 5 (A.V. S.Roberts) and 6 (M. K. Pratten) prepared colloid particles by, first,chelating ¹²⁵I and ¹⁴C to polyvinylpyrrolidone as a stabilizer, and thencoupling the result to colloid gold to use it as a bio-tracer. However,since radioisotopes such as ¹²⁵I and ¹⁴C are adsorbed onto soil andemits low energy of radiation, it is difficult to detect the behavior inthe soil sample, not to mention the flow in the industrial processing.

Accordingly, considering the fact that the measurement result with asingle radioactive particle particularly on the multi phase flow doesnot provide information about phase ratio, the present inventorsprepared heteronuclear radioisotope nanoparticle with core-shellstructure in which two different types of elements as the cores arecoated with SiO₂, to thus obtain information about the phase ratio onthe multi phase flow and calculate the volume ratio, and was confirmedthat the prepared nanoparticle can be used as a tracer to detect theflow behavior of the fluid, and completed the invention.

[Reference 1] S.-H Choi, Y.-P. Zhang, A.Gopalan, K.-P. Lee, H.-D. Kang,Preparation of Catalytically Efficient Precious Metallic Colloids byγ-Irradiation and Characterization, Colloids Surfaces A, 256, 165-170(2005).

[Reference 2] S.-D. Oh, B.-K. So, S.-H. Choi, A.Gopalan, K.-P. Lee, K.R. Yoon, I. S. Choi, Dispersing of Ag, Pd, and Pt—Ru alloy nanoparticleson single-walled carbon nanotubes by y-irradiation, Mater. Lett., 59,1121-1124 (2005).

[Reference 3] KR 10-2010-0034499 A 2010.04.01, p. 4, lines 19-24

[Reference 4] C.P. Winlove, J. Davis, A. Iacovides, A. Chabanel,Radioactive Gold Colloid as a Tracer of Macromolecules Transport,Biotechnology, 18, 569-578 (1981).

[Reference 5] A.V.S. Roberts, K. E. Williams, and J. B. LLoyd, “ThePinocytosis of ¹²⁵I-Labelled Poly(vinylpyrrolidone), [¹⁴C]Sucrose andColloidal [198Au]Gold by Rat Yolk Sac Cultured in vitro, Biochem. J.168, 239-244 (1977).

[Reference 6] M. K. Pratten, and J.B. Lloyd, Effects of Temperature,Metabolic Inhibitors and Some Other Factors on Fluid-Phase andAdsorptive Pinocytosisi by Rat Peritoneal Macrophages, Biochem. J., 180,567-571 (1979).

SUMMARY OF THE INVENTION

The present invention has been made to overcome the above-mentioneddisadvantages in the related art, and accordingly, an object of thepresent invention is to provide heteronuclear radioisotope nanoparticleof core-shell structure which is stable to be used as a tracer fordetecting a variation in the volume ratio through measurement of phaseratio of multi phase flow.

Another object of the present invention is to provide a method forpreparing said heteronuclear radioisotope nanoparticle of core-shellstructure. In one embodiment, Heteronuclear radioisotope nanoparticle ofcore-shell structure is provided, which may include a core comprisingtwo different radioisotopes selected from a group consisting of ¹⁹⁸Au,⁶³Ni, ^(110n)Ag, ⁶⁴Cu, ⁶⁰CO, ¹⁹²Ir and ¹⁰³Pd, and a shell comprisingSiO₂ surrounding the core. In another embodiment, a method for preparingHeteronuclear radioisotope nanoparticle of core-shell structure isprovided, which may include (step 1) preparing core of the heteronuclearnanoparticle by dispersing two different types of atoms selected from agroup consisting of Au, Ni, Ag, Cu, Co, Ir and Pd in water, andstabilizing the result with colloid stabilizer, (step 2) preparingnanoparticle with core-shell structure by coating the nanoparticle coreprepared at step 1 with SiO₂ repeatedly for several times; (step 3)removing the colloid stabilizer remaining in the core-shell structureprepared at step 2 by calcining the prepared nanoparticle, and (step 4)activating the nanoparticle within the core by irradiating neutron ontothe nanoparticle with the core-shell structure prepared at step 3.

According to the heteronuclear radioisotope nanoparticle of core-shellstructure of an embodiment, since two different radioisotopes areintegrated into one core, the nanoparticle have less oxidization oragglomeration compared to single nanoparticle, and accordingly providehigher safety. Further, since the Heteronuclear radioisotopenanoparticle of core-shell structure according to an embodiment emitheterogeneous gamma rays, the nanoparticle can be used as a tracer forthe purpose of detecting flow of fluid existing in a multi phase processwhich is operated under extreme condition such as high temperatureand/or high pressure operation, and for the detection of variation inthe volume ratio or evaluation of behavior characteristic of waterresource through phase ratio measurement.

The Heteronuclear radioisotope nanoparticle of core-shell structureaccording to an embodiment is coated with SiO₂ which is not activated bythe irradiation of neutron, agglomeration of nanoparticles due toremoval of colloid stabilizer can be prevented. Further, due to theminimum possibility that the remaining colloid stabilizer is activatedduring activation of the nanoparticle in the process such as removal ofcolloid stabilizer, the quantity and quality of the informationobtainable from the radiation of the radioisotope are ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of what is described herein will be moreapparent by describing certain exemplary embodiments with reference tothe accompanying drawings, in which:

FIG. 1 is a schematic view illustrating a process of preparingheteronuclear radioisotope nanoparticle of core-shell structureaccording to the present invention;

FIG. 2 is a TEM image of Au—Ag core nanoparticle stabilized withpolvinylpyrrolidone prepared at Example 1 according to the presentinvention, in which mole ratio of core nanoparticle (i.e., Au and Ag) is1:1;

FIG. 3 is a TEM image of Au—Ag@ SiO₂, which is the heteronuclearradioisotope nanoparticle of core-shell structure prepared at Example 1according to the present invention;

FIG. 4 is a TEM image of Au—Ni core nanoparticle stabilized withpolyvinylpyrrolidone prepared at Example 2 according to the presentinvention, in which mole ratio of core nanoparticle (i.e., Au and Ni) is1:1;

FIG. 5 is a TEM image of Au—Co core nanoparticle stabilized withpolyvinylpyrrolidone prepared at Example 3 according to the presentinvention, in which mole ratio of core nanoparticle (i.e., Au and Co) is1:1;

FIG. 6 is a TEM image of Au—Cu core nanoparticle stabilized withpolyvinylpyrrolidone prepared at Example 4 according to the presentinvention, in which mole ratio of core nanoparticle (i.e., Au and Cu) is1:1;

FIG. 7 is a TEM image of Au—Ir core nanoparticle stabilized withpolyvinylpyrrolidone prepared at Example 5 according to the presentinvention, in which mole ratio of core nanoparticle (i.e., Au and Ir) is1:1;

FIG. 8 is a result of EDS measurement of Au—Ag core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 1 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Ag) is 1:1;

FIG. 9 is a result of EDS measurement of Au—Ag@SiO₂, which is theheteronuclear radioisotope nanoparticle of core-shell structure preparedat Example 1 according to the present invention;

FIG. 10 is a result of EDS measurement of Au—Ni core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 2 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Ni) is 1:1;

FIG. 11 is a result of EDS measurement of Au—Co core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 3 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Co) is 1:1;

FIG. 12 is a result of EDS measurement of Au—Cu core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 4 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Cu) is 1:1;

FIG. 13 is a result of EDS measurement of Au—Ir core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 5 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Ir) is 1:1;

FIG. 14 is a result of ELS measurement of Au—Ag core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 1 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Co) is 1:1, and average granularity (D)=192.4 nm;

FIG. 15 is a result of ELS measurement of Au—Ag Au—Ag@SiO₂, which is theheteronuclear radioisotope nanoparticle of core-shell structure preparedat Example 1 according to the present invention, in which averagegranularity (D)=111.1 nm;

FIG. 16 is a result of ELS measurement of Au—Co core nanoparticlestabilized with polvinylpyrrolidone prepared at Example 3 according tothe present invention, in which mole ratio of core nanoparticle (i.e.,Au and Co) is 1:1, and average granularity (D)=107.2 nm;

FIG. 17 is a result of UV-visible spectrophotometer of Au—Ag@SiO2 whichis heteronuclear radioatice isotope of core-shell structure prepared atExample 1 according to the present invention; and

FIG. 18 is a result of NAA measurement of Au—Ag@SiO2 which isheteronuclear radioisotope of core-shell structure prepared at Example 1according to the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the present invention will be explained in detail below.

According to an embodiment, heteronuclear radioisotope nanoparticle ofcore-shell structure is provided, in which core of two different typesof radioisotopes is coated with SiO₂.

In one embodiment, the two different types of radioisotopes may includeone selected from the radioisotopes including ¹⁹⁸Au, ⁶³Ni, ^(110m)Ag,⁶⁴Cu, ⁶⁰Co,¹⁹²Ir, ¹⁰³Pd. In a preferred embodiment, the cores of theHeteronuclear radioisotope nanoparticle may use a combination of ¹⁹⁸Auand any particle selected from the rest of the group excluding ¹⁹⁸Au,but not limited thereto.

In one embodiment, a method for preparing Heteronuclear radioisotopenanoparticle of core-shell structure is provided, which may include:

(step 1) preparing core of the heteronuclear nanoparticle by dispersingtwo different types of atoms selected from a group consisting of Au, Ni,Ag, Cu, Co, Ir and Pd in water, and stabilizing the result with colloidstabilizer;

(step 2) preparing nanoparticle with core-shell structure by coating thenanoparticle core prepared at step 1 with SiO₂ repeatedly for severaltimes;

(step 3) removing the colloid stabilizer remaining in the core-shellstructure prepared at step 2 by calcining the prepared nanoparticle; and

(step 4) activating the nanoparticle within the cores by irradiatingneutron onto the nanoparticle with the core-shell structure prepared atstep 3.

The respective steps of the method for preparing Heteronuclearradioisotope nanoparticle of core-shell structure according to thepresent invention will be explained in greater detail below.

Step 1: Preparation of core of heteronuclear nanoparticle

In one embodiment, step 1 relates to preparing core of the heteronuclernanoparticle by dispersing two difference types of particles in waterand stabilizing the result with colloid stabilizer.

At step 1, the two different types of raw material for nanoparticle maybe selected from Au, Ni, Ag, Cu, Co, Ir or Pd. The raw material may beused in purified form, or used along with all the compounds containedtherein.

At step 1, efficiency of dispersion may be enhanced by use of colloidstabilizer which prevents agglomeration among nanoparticles dispersed inwater and provides stabilization effect.

Any stabilizer may be used as the colloid stabilizer, as long as thestabilizer is capable of blocking aggregation among the colloidparticles and enhancing dispersion efficiency to thus providestabilization of the particle, but in one preferred embodiment,polyvinylpyrrolidone may be used.

In one embodiment, step 1 may additionally include a step for removingoxygen present in the fluid, by performing N₂ purging to preventoxidation of the matters constituting the fluid for reaction whichcontains the two different types of elements.

Further, step 1 may enhance stabilization effect of the heteronuclearnanoparticle by use of colloid stabilizer such as polyvinylpyrrolidone,by irradiating gamma radiation onto the colloid fluid. Time and dose ofirradiating gamma radiation may be adjusted appropriately depending onneed and according to the raw material of the core.

Step 2: Preparation of heteronuclear nanoparticle with core-shellstructure

Next, in step 2, nanoparticle with core-shell structure is prepared bycoating the nanoparticle core prepared at step 1 with SiO₂ repeatedlyfor several times.

Accordingly, as SiO₂ is coated on the nanoparticle core prepared at step1, the nanoparticle with core-shell structure in which core of twodifferent types of elementals is covered by SiO₂ shell, is prepared.

To be specific, a certain amount of colloid fluid in which heteronuclearnanoparticle core are dispersed and which is stabilized with colloidstabilizer in step 1 may be prepared, mixed with a solvent such asisopropanol and added with a small amount of ammonia solution. Amaterial to provide SiO₂ as a shell may then be added to coat around thecore. The material to provide SiO₂ may include, for example, tetraethoxyorthosilicate (TEOS). The thickness of the shell may be adjusted byrepeatedly adding TEOS for several times.

Step 3: Removal of colloid stabilizer

In step 3, colloid stabilizer is removed from the heteronuclearnanoparticle of core-shell structure which is prepared in step 2.

In step 3, the colloid stabilizer may be removed by calcining undernitrogen flow. The calcination temperature may be adjusted in accordancewith the type of the colloid stabilizer used. By way of example, ifpolyvinylpyrrolidone is used as the colloid stabilizer, the calcinationtemperature may preferably be 500-600° C.

The nanoparticle after the calcining is in powder form from whichstabilizer is removed. As explained above, the remaining colloidstabilizer is removed to ensure quality and quantity of the componentthat can be obtained in the radiation detection emitted from theradioisotope, because if the colloid stabilizer is left in theheteronuclear nanoparticle, there is the possibility that the colloidstabilizer can also be activated when the nanoparticle is activated inthe following step.

Step 4: Preparation of Heteronuclear radioisotope nanoparticle ofcore-shell structure

Next, in step 4, the nanoparticle of core-shell structure prepared instep 3 is activated.

The activation may be performed by irradiating neutron in the nuclearreactor on the heteronuclear nanoparticle of core-shell structureprepared in step 3.

Since the heteronuclear nanoparticle of core-shell structure activatedin step 4 according to the present invention emits specific radiationemitted from the respective nuclides, the nanoparticle can be used forvarious purposes.

Furthermore, in one embodiment, Heteronuclear radioisotope nanoparticleof core-shell structure isprovided, which can be used as a tracer forthe purpose of detecting movement of the fluid existing in the multiphase process driven under extreme conditions including high temperatureand/or high pressure, or used for the purpose of evaluating the behaviorof the water resource.

Unlike the homonuclear nanoparticle, the nanoparticle in one embodimentof the present invention has different types of heteronuclearradioisotopes as the core and thus can emit gamma ray of differentcharacteristics. Accordingly, it is possible to measure the respectivephrase ratios by analyzing information about the movements of the multiphase fluid particularly existing in high temperature and high pressureindustrial processing which does not easily permit access. Further, itis also possible to calculate the volume ratio based on the informationabout the phase ratio of the multi phase fluid.

In general, radiation attenuation coefficient of a matter changes inaccordance with the radiation energy. If two types of radiation sourcesthat emit two different gamma energies are used, it is possible toobtain the phase ratio of the mixture. The fluid compound rate (α_(i))according to two types of gamma ray energy absorption can be calculatedby:

$\begin{matrix}{{I_{m}(e)} = {{I_{\upsilon}(e)}{\exp \left\lbrack {- {\sum\limits_{i = 1}^{3}{\alpha_{i}{\mu_{i}(e)}d}}} \right\rbrack}}} & \left\lbrack {{Mathematical}\mspace{14mu} {formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

where, I_(u)(e) denotes initial value of the system which indicates theradiation amount detected in a state where the system is empty. μ_(i)denotes linear attenuation coefficient with respect to multi phase. Byway of example, if two gamma ray energies e₁, e₂ with large differencesof attenuation coefficients are selected from the respective phases ofthe multi phase fluid consisting of water, oil and gas, two formulae canbe obtained. Since 1 is the sum of total phase ratios of the mixture,the third mathematical formula can be obtained accordingly.

If the heteronuclear radioisotope nanoparticle of core-shell structureprepared according to an embodiment of the present invention is used asa tracer for the movement of multi phase fluid, since the corescomprising two different types of radioisotopes, two gamma ray energies,i.e., ¹⁹⁸Au(e₁) and ^(110m)Ag(e₂) are selected to obtain twomathematical formulae. The third mathematical formula can be obtainedbased on the fact that the sum of the total phase ratios of the mixtureis 1.

Referring to the above examples, the three formulae obtained throughmathematical formula 1 by selecting two gamma ray energies e₁ and e₂from the multi phase fluid consisting of water, oil and gas may beexpressed as follows:

$\begin{matrix}{{\begin{bmatrix}{R_{w}\left( e_{1} \right)} & {R_{o}\left( e_{1} \right)} & {R_{g}\left( e_{1} \right)} \\{R_{w}\left( e_{2} \right)} & {R_{o}\left( e_{2} \right)} & {R_{g}\left( e_{2} \right)} \\1 & 1 & 1\end{bmatrix}\begin{bmatrix}\alpha_{w} \\\alpha_{o} \\\alpha_{g}\end{bmatrix}} = \begin{bmatrix}{R_{m}\left( e_{1} \right)} \\{R_{m}\left( e_{2} \right)} \\1\end{bmatrix}} & \left\lbrack {{Mathematical}\mspace{14mu} {formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

where, R_(W), R₀, R_(g) and R_(m) are log values of detected radiationamounts with respect to water, oil, gas and mixture by the two gamma rayenergies e₁ and e₂, respectively. R_(W), R₀, R_(g) which are necessaryfor the calculation, are obtained by the correction process in which thesystem is filled with the corresponding phases to 100% and measured. Inactual measurement test, ratios α_(W), α_(o), α_(g) of the respectivephases may be obtained by obtaining gamma ray energies R_(m)(e₁) andR_(m)(e₂) and applying these to mathematical formula 2.

By applying the above-explained example, it is possible to measure thegamma ray energy under the following condition, to obtain informationabout the phase ratio of the movement of the multi phase fluid by usingheteronuclear radioisotope nanoparticle of core-shell structure. First,detected radiation amount I_(u)(e) is measured as the initial value inthe empty system. Then, water phase ratio α_(w), oil phase ratio α_(O),and gas phase ratio α_(g) in the mixture state are obtained by applyingthe log values of the measured values of ¹⁹⁸Au and ^(110m)Ag gamma rayenergies emitted from: system of 100% water, system of 100% oil, andsystem of 100% gas to mathematical formula 2. From the above, it ispossible to obtain volume ratios of the respective fluids constructingmulti phase fluid.

Hereinbelow, an embodiment of the present invention will be explained ingreater detail. However, an embodiment is not limited to specificexamples only.

EXAMPLE 1 Step 1. Preparation of Heteronuclear Nanparticle Core byRadiation Reduction

0.19 mmol of HAuCl₄3H₂O (0.078 g) and AgNO₃(0.033 g) were dispersed intertiary distilled water (376 ml) so that Au and Ag were at 1:1 moleratio. To the fluid in which HAuCl₄3H₂O and AgNO₃ were dispersed,polyvinylpyrrolidone (1 g) as colloid stabilizer and isopropanol (24 ml)were added and mixed. The reacted fluid underwent nitrogen purging toremove oxygen existing in the solution, and ⁶⁰Co-γ was irradiated for 3hr, in a manner in which the total dose of radiation was 30 kGy. Thereacted fluid was yellow before reaction, and turned into purple afterirradiation so that Au—Ag nanoparticle, which was stabilized withpolyvinylpyrrolidone, can be prepared.

Step 2. Preparation of Heteronuclear Nanonparticle with Core-ShellStructure by Sol-Gel Reaction

Colloid fluid (4 ml), in which the Au—Ag nanoparticle core stabilizedwith polyvinylpyroolidone and prepared in step 1, was mixed withisopropanol (20 ml), 30 wt. % ammonia solution (0.5 ml) was added to thereaction vessel, and tetraetoxy orthosilicate (TEOS) (10 mmol) wasadded, and left to react for 2 hr at room temperature. As a result,nanoparticle (Au—Ag@SiO) having Au—Ag core and SiO₂ shell was prepared.

Step 3. Removal of Colloid Stabilizer

Polybvinylpyrrolidon, which is colloid stabilizer, was completelyremoved as the nanoparticle (Au—Ag@SiO₂) prepared in step 2 was calcinedat 500° C. under nitrogen flow.

Step 4. Preparation of Heteronuclear Radioisotope Nanoparticle ofCore-Shell Structure

Radioisotope nanoparticle Au—Ag@SiO₂(20 mg) having Au—Ag core and SiO₂shell was prepared, by irradiating neutrons to the nanoparticle(¹⁹⁸Au-^(110m)Ag@SiO₂) prepared in step 3 in the nuclear reactor(Hanaro, neutron irradiation: 2.8×10¹³/cd s) designed for research atthe Korea Atomic Energy Research Institute.

Example 2

The radioisotope nanoparticle having Au—Ni core and SiO₂ shell wasprepared in the same manner as that in Example 1, except that Ni insteadof Ag was used as the nuclides of the nanoparticle core and 0.19 mmol ofHAuCl₄3H₂O (0.078 g) and Ni(NO₃)₂6H₂O (0.055 g) were used to 1:1 moleratio.

Example 3

The radioisotope nanoparticle having Au—Co core and SiO₂ shell wasprepared in the same manner as that in Example 1, except that Co insteadof Ag was used as the nuclides of the nanoparticle core and 0.19 mmol ofHAuCl₄3H₂O (0.078 g) and CoCl₂6H₂O (0.045 g) were used to 1:1 moleratio.

Example 4

The radioisotope nanoparticles having Au—Cu cores and SiO₂ shells wereprepared in the same manner as that in Example 1, except that Cu insteadof Ag was used as the nuclides of the nanoparticle cores and 0.19 mmolof HAuCl₄3H₂O (0.078 g) and CuCl₂2H₂O (0.032 g) were used to 1:1 moleratio.

Example 5

The radioisotope nanoparticle having Au—Ir core and SiO₂ shell wasprepared in the same manner as that in Example 1, except that Ir insteadof Ag was used as the nuclides of the nanoparticle core and 0.19 mmol ofHAuCl₄3H₂O (0.078 g) and IrCl₄.xH₂O (0.063 g) were used to 1:1 moleratio.

Analysis:

1. Transmission Electron Microscopy (TEM)

Nanoparticles prepared according to Examples 1 to 5 of the presentinvention were measured with TEM (JEOL, JEM-2010F, Japan), and theresults are provided on FIGS. 2 to 7. Referring to FIG. 3, Au—Agheteronuclear nanoparticle of Example 1 prepared according to anembodiment of the present invention include approximately 40 nm core andapproximately 30 nm shell (FIG. 2: Example 1, FIG. 3: Example 1, FIG. 4:Example 2, FIG. 5: Example 3, FIG. 6: Example 4, FIG. 7: Example 5). Theresults indicated that the core-shell nanoparticle was preparedsuccessfully.

2. Nanoparticle component analysis using Energy Dispersive Spectroscopy(EDS)

Core or core-shell nanoparticles prepared according to Examples 1 to 5were measured using EDS (JEM-2010F, Japan), and the results are providedon FIGS. 8 to 13 (FIG. 8: Example 1, FIG. 9: Example 1, FIG. 10: Example2, FIG. 11: Example 3, FIG. 12: Example 4, FIG. 13: Example 5). Theresults indicated that the core-shell nanoparticle was preparedsuccessfully.

3. Nanoparticle Analysis using Grain Size Measurement (ELS)

Core or core-shell nanoparticles prepared according to Examples 1 and 3were measured using ELS (ELS-8000, Otsuka Co., Japan), and the resultsare provided on FIGS. 14 to 16 (FIG. 14: Example 1, FIG. 15: Example 1,FIG. 16: Example 3). The results indicated that the core-shellnanoparticle was prepared successfully.

4. Core-Shell Nanoparticle Analysis using UV-Visible Spectrophotometer

Core-shell nanoparticle prepared according to Example 1 was measuredusing UV-Vis Spectrophotometer (Shimadzu UV-3101PC digitalspectrophotometer, Kyoto, Japan), and the results are provided on FIG.17. The results indicated that the core-shell nanoparticle was preparedsuccessfully.

5. Core-Shell Nanoparticle Analysis using Neutron Activation Analysis(NAA)

Core-shell nanoparticle prepared according to Example 1 was measuredusing NAA (HPGe detector, EG&G Ortec, 25% relative efficiency, FWHM 1.85keV at 1332 keV of ⁶⁰Co), and the results are provided on FIG. 18. Theresults confirmed that no radioactive nuclides were generated except forAu and Ag by the neutron irradiation.

The foregoing exemplary embodiments and advantages are merely exemplaryand are not to be construed as limiting the present invention. Thepresent teaching can be readily applied to other types of apparatuses.Also, the description of the exemplary embodiments of the presentinventive concept is intended to be illustrative, and not to limit thescope of the claims, and many alternatives, modifications, andvariations will be apparent to those skilled in the art.

What is claimed is:
 1. A Heteronuclear radioisotope nanoparticle ofcore-shell structure, comprising a core comprising two differentradioisotopes selected from a group consisting of ¹⁹⁸Au, ⁶³Ni,^(110m)Ag, ⁶⁴Cu, ⁶⁰Co, ¹⁹²Ir and ¹⁰³Pd, and a shell comprising SiO₂surrounding the core.
 2. The heteronuclear radioisotope nanoparticle ofcore-shell structure as set forth in claim 1, wherein the core comprisea combination of ¹⁹⁸Au and one of the rest of the group except ¹⁹⁸Au. 3.The heteronuclear radioisotope nanoparticle of core-shell structure asset forth in claim 1, wherein the two different radioisotepes of thecore emit radiations distinguished from each other.
 4. A method forpreparing the heteronuclear radioisotope nanoparticle of core-shellstructure as set forth in claim 1, the method comprising: (step 1)preparing cores of the heteronuclear nanoparticle by dispersing twodifferent types of atoms selected from a group consisting of Au, Ni, Ag,Cu, Co, Ir and Pd in water, and stabilizing the result with colloidstabilizer; (step 2) preparing nanoparticle with core-shell structure bycoating the nanoparticle core prepared at step 1 with SiO₂ repeatedlyfor several times; (step 3) removing the colloid stabilizer remaining inthe core-shell structure prepared at step 2 by calcining the preparednanoparticle; and (step 4) activating the nanoparticle within the coreby irradiating neutron onto the nanoparticle with the core-shellstructure prepared at step
 3. 5. The method as set forth in claim 4,comprising applying the colloid stabilizer to the nanoparticle byirradiating radiation to stabilize the nanoparticle core of step
 1. 6.The method as set forth in claim 4, wherein the colloid stabilizer ofstep 1 is polyvinylpyrrolidone.
 7. The method as set forth in claim 4,wherein the calcining for removing the colloid stabilizer in step 3 isperformed under nitrogen flow at 500-600° C.
 8. The heteronuclearradioisotope nanoparticle of core-shell structure as set forth in claim1, which is used as a tracer for the purpose of detecting movement ofmulti phase fluid existing in a process operated under extreme conditionincluding high temperature and/or high pressure, or for the purpose ofevaluating behavior of water resource.
 9. The heteronuclear radioisotopenanoparticle of core-shell structure as set forth in claim 8, whereinratios of respective phases are measured through flow detection on themulti phase fluid, and information regarding volume ratio of the multiphase fluid is obtained therefrom.
 10. The heteronuclear radioisotopenanoparticle of core-shell structure as set forth in claim 8, whereinthe fluid existing in the process is dual phase fluid.